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<head>
    <meta charset="UTF-8">
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    <title>Document</title>
    <style>
        .box {
            width: 100px;
            height: 100px;
            text-align: center;
            line-height: 100px;
            background-color: #333;
            color: #ffc;
            text-shadow: 0 0 .1em, 0 0 .3em;
        }

        a {
            font-size: 25px;
            background: #333;
            color: white;
            transition: 1s;
            text-decoration: none;
        }

        a:hover {
            color: transparent;
            text-shadow: 0 0 .1em white, 0 0 .3em white;
            /* filter: blur(.1em); (部分浏览器适用)*/
        }
    </style>
</head>

<body>
    <div class="box">
        <a href="#">GLOW</a>
    </div>
</body>

</html>